Flexible and Transparent Paper-Based Ionic Diode Fabricated from Oppositely Charged Microfibrillated Cellulose

Recently, organic diodes have attracted great research interest because of their unique applications in flexible electronics. Electronic paper is one of the most attractive organic electronic devices. Hereby, we report a transparent, flexible, ionic diode paper made of two oppositely charged microfibrillated cellulose (MFC) sublayers. The current rectification ratio is around 15 at +/- 5 V and exhibits good repeatability at room temperature. Instead of forming a depletion region to rectify current, this paper diode uses asymmetric charge distribution to selectively control the ion diffusion direction. The asymmetric charge distribution inside the diode paper can selectively transport cations and anions under positive and negative bias, to allow an electric current to pass in one direction while being blocked in the opposite direction. Although the mechanism is quite different from semiconductor-based p-n junction, the phenomenon turns out to be very similar. It was found that the moisture content, thickness of paper, and scanning frequency will influence the performance of the diode paper. All these factors are closely related to the ionic characteristics of the diode.